Detect and handle the case of our own typo correction extension being installed in parallel

lib/main.js

 /*
  * This Source Code is subject to the terms of the Mozilla Public License
  * version 2.0 (the "License"). You can obtain a copy of the License at
  * http://mozilla.org/MPL/2.0/.
  */
 
 /**
  * @fileOverview Starts up Adblock Plus
  */
 
 Cu.import("resource://gre/modules/XPCOMUtils.jsm");
 Cu.import("resource://gre/modules/Services.jsm");
+Cu.import("resource://gre/modules/AddonManager.jsm");
 
 let {TimeLine} = require("timeline");
 
 TimeLine.enter("Adblock Plus startup");
 let {Prefs} = require("prefs");
 TimeLine.log("Done loading preferences");
 registerPublicAPI();
 TimeLine.log("Done registering public API");
 require("filterListener");
 TimeLine.log("Done loading filter listener");
 require("contentPolicy");
 TimeLine.log("Done loading content policy");
 require("synchronizer");
 TimeLine.log("Done loading subscription synchronizer");
 require("sync");
 TimeLine.log("Done loading sync support");
 require("ui");
 TimeLine.log("Done loading UI integration code");
-if (!Prefs.correctTyposAsked || (Prefs.correctTyposAsked && Prefs.correctTypos))
+(function()

[Wladimir Palant, 2012/11/19 07:30:02]

Please move that entire logic into a separate typoBootstrap.js module.

 {
-  require("typoFixer");
-  TimeLine.log("Done loading typo correction");
-}
-else
-{
-  let onPrefChange = function(name)
+  let urlfixerID = "{0fa2149e-bb2c-4ac2-a8d3-479599819475}";
+  let isTypoCorrectionEnabled;
+  let typoFixerLoaded = false;
+  
+  function enableTypoCorrection()
   {
-    if (name == "correctTypos")
+    if (isTypoCorrectionEnabled)
+      return;
+    
+    if (typoFixerLoaded)
+    {
+      require("typoFixer").attachWindowObserver();
+    }
+    else
     {
       require("typoFixer");
-      Prefs.removeListener(onPrefChange);
+      typoFixerLoaded = true;
+    }

[Wladimir Palant, 2012/11/19 07:30:02]

How about just doing require("typoFixer").attachWindowObserver() here and
leaving it up to attachWindowObserver to figure out whether it needs to do
anything? You should be able to save some of unnecessary state variables and
simplify the logic then.

+    
+    isTypoCorrectionEnabled = true;
+  }
+  
+  function disableTypoCorrection()
+  {
+    if (!isTypoCorrectionEnabled)
+      return;
+    
+    if (typoFixerLoaded)
+    {
+      require("typoFixer").detachWindowObserver();
+    }

[Wladimir Palant, 2012/11/19 07:30:02]

How about just doing require("typoFixer").detachWindowObserver() here and
leaving it up to detachWindowObserver to figure out whether it need to do
anything? You should be able to save some of unnecessary state variables and
simplify the logic then.

+    
+    isTypoCorrectionEnabled = false;
+  }
+  
+  function checkAddonStatusAndEnable()
+  {
+    AddonManager.getAddonByID(urlfixerID, function(addon)
+    {
+      checkAndEnable(addon && !addon.userDisabled);
+    });
+  }
+  
+  function checkAndEnable(isInstalledAndEnabled)
+  {
+    if (isInstalledAndEnabled)
+    {
+      disableTypoCorrection();
+    }
+    else
+    {
+      if (!Prefs.correctTyposAsked || (Prefs.correctTyposAsked && Prefs.correctTypos))

[Wladimir Palant, 2012/11/19 07:30:02]

This logic seems wrong. If typo corrections are disabled then we have no reason
to do anything - including watching URL Fixer. We should check the preferences
first and only install the add-on listener if we have a reason for that.

+      {
+        enableTypoCorrection();
+      }
+      else if (!typoFixerLoaded)
+      {
+        function onPrefChange(name)
+        {
+          if (name == "correctTypos")
+          {
+            checkAddonStatusAndEnable();
+            Prefs.removeListener(onPrefChange);
+          }
+        }
+        
+        Prefs.addListener(onPrefChange);
+      }
     }
   }
   
-  Prefs.addListener(onPrefChange);
-}
+  let addonListener = {
+    onEnabling: function(addon, needsRestart)
+    {
+      if (addon.id == urlfixerID)
+        checkAndEnable(true);
+    },
+    onDisabled: function(addon)
+    {
+      if (addon.id == urlfixerID)
+        checkAndEnable(false);
+    },
+    onInstalling: function(addon, needsRestart)
+    {
+      if (addon.id == urlfixerID)
+        checkAndEnable(true);
+    },
+    onUninstalled: function(addon)
+    {
+      if (addon.id == urlfixerID)
+        checkAndEnable(false);
+    },
+    onOperationCancelled: function(addon)
+    {
+      if (addon.id == urlfixerID)
+        checkAddonStatusAndEnable();

[Wladimir Palant, 2012/11/19 07:30:02]

Please ignore this call - URL Fixer is restartless, all operations are executed
immediately.

+    }
+  }
+  AddonManager.addAddonListener(addonListener);
+  
+  checkAddonStatusAndEnable();
+})();
+TimeLine.log("Done loading typo correction");
 TimeLine.leave("Started up");
 
 function registerPublicAPI()
 {
   let {addonRoot} = require("info");
 
   let uri = Services.io.newURI(addonRoot + "lib/Public.jsm", null, null);
   if (uri instanceof Ci.nsIMutable)
     uri.mutable = false;
 
@@ skipping 12 matching lines @@
 
   let registrar = Components.manager.QueryInterface(Ci.nsIComponentRegistrar);
   registrar.registerFactory(classID, "Adblock Plus public API URL", contractID, factory);
 
   onShutdown.add(function()
   {
     registrar.unregisterFactory(classID, factory);
     Cu.unload(uri.spec);
   });
 }